October 7, 2003
Elvia Thompson
Headquarters, Washington
(Phone: 202/358-1696)
Krishna Ramanujan
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 607/273-2561)
Mark Shwartz
Stanford News Service, Calif.
(Phone: 650/723-9296)
RELEASE: 03-315
ANTARCTIC PENGUINS THRIVE IN OCEAN "OASES"
Image left: In eastern Antarctica, more than 90 percent of all Adelie
Penguin colonies live next to coastal polynyas.
NASA satellite data was used for the first time to analyze the biology
of hot spots along the coast of Antarctica. The biological oases are
open waters, called polynyas, where blooming plankton support the
local food chain.
The research found a strong association between the well being of
Adelie Penguin populations in the Antarctic and the productivity of
plankton in the polynyas. Polynyas are areas of open water or reduced
ice cover, where one might expect sea ice. They are usually created
by strong winds that blow ice away from the coast leaving open areas,
or by gaps appearing on the ocean's surface, when flowing ice gets
blocked by an impediment, like an ice shelf.
The Antarctic waters are rich in nutrients. The lack of ice, combined
with shallow coastal waters, provides the top layers of the ocean
with added sunlight, so polynyas offer ideal conditions for
phytoplankton blooms. Because the ice around polynyas is thin in the
early spring when the long Austral day begins, they are the first
areas to get strong sunlight. The open waters retain more heat,
further thinning ice cover and leading to early, intense, and
short-lived plankton blooms. These blooms feed krill, a tiny,
shrimp-like animal, which in turn are eaten by Adelie Penguins,
seabirds, seals, whales, and other animals.
Although relatively small in area, coastal polynyas play a
disproportionately important role in many physical and biological
processes in Polar Regions. In eastern Antarctica, more than 90
percent of all Adelie Penguin colonies live next to coastal polynyas.
Polynya productivity explains, to a great extent, the increase and
decrease in penguin population.
"It's the first time anyone has ever looked comprehensively at the
biology of the polynyas," said Kevin Arrigo, assistant professor of
Geophysics at Stanford University, Stanford, Calif. "No one had any
idea how tightly coupled the penguin populations would be to the
productivity of these polynyas. Any changes in production within
these polynyas are likely to lead to dramatic changes in the
populations of penguins and other large organisms," Arrigo said.
The study, which appeared in a recent issue of the Journal of
Geophysical Research, used satellite-based estimates to look at
interannual changes in polynya locations and sizes; abundance of
microscopic free-floating marine plants called phytoplankton, which
are the base of the polar ocean food chain; and the rate at which
phytoplankton populations thrive. Covering five annual cycles from
1997 to 2002, 37 coastal polynya systems were studied.
The largest polynya studied was located in the Ross Sea (396,500
square kilometers or 153,100 square miles; almost the size of
California). The smallest was located in the West Lazarev Sea (1,040
square kilometers or 401.5 square miles). Most polynyas, at their
maximum area in February, were less than 20,000 square kilometers
(7,722 square miles).
Data from NASA's Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and
NOAA's Advanced Very High Resolution Radiometer (AVHRR) provided
weekly measurements of chlorophyll and temperature that were used in
a computer model to estimate phytoplankton productivity. The
researchers found, taken together, the Ross Sea, Ronne Ice Shelf,
Prydz Bay, and Amundsen Sea polynyas were responsible for more than
75 percent of total plankton production.
The researchers were surprised to find how closely connected the
Adelie Penguins were to the productivity of their local polynyas. The
more productive polynyas supported larger penguin populations. The
more abundant krill fed more penguins, and the birds had shorter
distances to go to forage, which reduced exposure to predators and
other dangers.
The NASA Oceanography Program, the National Science Foundation, and
the U.S. Department of Energy funded this research. NASA's Earth
Science Enterprise is dedicated to understanding the Earth as an
integrated system and applying Earth System Science to improve
prediction of climate, weather, and natural hazards using the unique
vantage point of space.
For information about the research and images on the Internet, visit:
http://www.gsfc.nasa.gov/topstory/2003/0930penguins.html
For information about Adelie Penguins on the Internet, visit:
http://www.aad.gov.au/default.asp?casid=1654
-end-